Largest Map of Part of the Universe

Largest Map of Part of the Universe.

What you are looking at in the above photo is one slice through the map of the large-scale structure of the Universe. Each dot in this picture indicates the position of a galaxy 6 billion years into the past. The image covers about 1/20th of the sky, a slice of the Universe 6 billion light-years wide, 4.5 billion light-years high, and 500 million light-years thick. Color indicates distance from Earth, ranging from yellow on the near side of the slice to purple on the far side. Galaxies are highly clustered, revealing superclusters and voids whose presence is seeded in the first fraction of a second after the Big Bang. This image contains 48,741 galaxies, about 3% of the full survey dataset. Grey patches are small regions without survey data.

Largest Map of Part of the UniverseA collaboration of hundreds of scientists released the “largest-ever, three-dimensional map of distant galaxies” with over 1.2 million spots as a part of the Baryon Oscillation Spectroscopic Survey (BOSS) program using a telescope in New Mexico, according to a press release from Brookhaven National Lab. The map isn’t for wanderers; scientists are trying to understand some of the universe’s unexplained properties, like what dark matter and dark energy are. Understanding those things requires a three-dimensional map bigger and looking Largest Map of Part of the Universefurther out than any map scientists have made prior. “Up until fifty or so years ago, scientists more or less understood the universe, but the discovery of dark matter and dark energy showed we don’t really understand most of it, since they make up around 95 percent of the stuff in the universe,” said BOSS’ principal investigator David Schlegel from Lawrence Berkeley National Lab.

If you look at the map, you’ll see a web of galaxies and places where dots clump. Dark matter still feels gravity’s pull, so galaxies align themselves along the webs and clumps of dark Largest Map of Part of the Universematter. We can detect dark energy too. When we look into space, really distant things we’d expect to look white actually look red; they’ve been redshifted. That’s because their light rays have stretched out, because the space itself the light travels through expands, like a stretched-out tattoo on someone who’s gaining a lot of weight. By measuring really far away things, we found out that the universe wasn’t just expanding, but the rate it expanded was actually speeding up.

In one theory of the universe, there’s a single number called the “cosmological constant” that says dark energy is a uniform thing permeating the universe and making it expand. Some physicists were hoping that a larger map would show the cosmological constant’s value changing in different places, rather than just being a single number everywhere, but the single number stuck throughout the swath of the universe covered by BOSS’ results. Schlegel thought theoretical physicists might be a little pigeonholed by the results, since they can do more with varying numbers than a single constant.

Largest Map of Part of the UniverseThe BOSS experiment is about more than just dark energy, though, pointed out Anže Slosar, Brookhaven National Lab and BOSS cosmologist. The experiment will also help pinpoint the mass of the neutrino particle. Soon, other experiments like the larger Dark Energy Spectroscopic Instrument (DESI) on a telescope at Kitt Peak in Arizona will pick up where the BOSS experiment leaves off. But Slosar was most excited about how intertwined our physical experiences on Earth are with the rest of the universe. “The fact that it’s the same fundamental laws that guide GPS satellites all the way down to one second after the big bang is pretty mindblowing,” he said.

Credit: Ryan F. Mandelbaum for Popsci (Abridged) 15 July 2016